The need to develop measures that tap into constructs of interest to social work, refine existing measures, and ensure that measures function adequately across diverse populations of interest is critical. Item response theory (IRT) is a modern measurement approach that is increasingly seen as an essential tool in a number of allied professions. IRT-based measurement uses a model-based approach that has several analytical and explanatory advantages over classical test theory. In particular, IRT-based techniques facilitate the process of specific item selection, allow for increased measurement precision with fewer items, and provide greater capacity for understanding and accounting for measurement bias across diverse populations. A survey of the top (as rated by impact factor) 20 social work journals revealed that few measurement articles in the social work literature use IRT or other modern measurement approaches. The benefit of incorporating more IRT-based approaches for developing, refining, and ensuring the application of measures to diverse populations is discussed.
KEY WORDS: bias; classical test theory; item response theory; measurement; social work
The state of measurement within the social work literature is integrally related to knowledge base development and, ultimately, the extent to which research is able to meaningfully inform practice (Holden, Nizza, & Weissman, 1995). Scholarship highlights at least three measurement-related research domains within the field of social work. The first concerns the development of valid and reliable measures that capture the diverse set of phenomena relevant to social work, particularly those phenomena that may not be adequately represented by existent standardized instruments. The second is the assessment and validation of such measures. In particular, high-quality intervention research hinges on the validity and reliability of measures used to assess outcomes (Rosen, Proctor, & Staudt, 1999).Third, a growing body of literature challenges the extent to which well-validated measures adequately account and adjust for within- and across-population sources of diversity (see Ramirez, Ford, Stewart, & Teresi, 2005; Snowden, 2003), and such concerns are highly salient to social work's commitment to diversity-sensitive and -responsive research and practice.
During the 1980s and 1990s, social work researchers outlined the relative benefits of item response theory (IRT) over classical test theory (CTT) measurement models, calling explicitly for IRT-based models' increased utilization to address measurement problems in social work research (DeRoos & Allen-Meares, 1993, 1998; Nugent & Hankins, 1989,1992). Indeed, IRT models have largely subsumed CTT approaches within a wide range of allied fields and disciplines (for example, medicine, psychology, nursing, public health, education) (see Dunn, Resnicow, & Klesges, 2006; Embretson & Reise, 2000; Fries, Bruce, & Cella, 2005; Lord, 1980; Ware, Bjorner, & Kosinski, 2000).
Given early interest among social work researchers and the recent proliferation of IRT methods within other applied social sciences, our overall objective in the present study was to assess the extent to which these methods are represented within social work research. This review thus realizes three overlapping aims. First, it provides a description and comparison of IRT and CTT models and outlines the potential contributions of IRT methods to social work scholarship; it also briefly discusses IRT more generally as a latent variable model and its overlap with confirmatory factor analytic (CFA) and multi-level modeling methods. Second, it presents the results of a structured review assessing the penetration of IRT-based methods into the field of social work as reflected in key social work research journals. Third, using these results as a launching point, we highlight particular lines of inquiry within social work research where the application of IRT methods would likely yield substantial innovation. …